The present invention relates generally to a method of coating and a shield for a component. In particular, the present invention relates to a photochemical edge shield that protects, for example, cooling slots of a vane of a gas turbine engine during a ceramic coating process.
A gas turbine engine includes alternating rows of rotary airfoils or blades and stationary airfoils or vanes. Each vane includes cooling slots that allow air to enter and cool the vane during use. The vanes are usually made of nickel superalloy and are commonly coated with a ceramic coating to provide a thermal barrier.
During the ceramic coating process, the ceramic coating can flow into and clog the cooling slots. If this occurs, the cooling effect of the cooling slots can decrease. A shield has been employed to cover the cooling slots and prevent the ceramic coating from entering the cooling slots during ceramic coating process. The shield of the prior art includes two projections that each fit into a corresponding slot in the airfoil to locate the shield relative to the airfoil. The projections are located at opposite ends of the shield, and a curved edge extends between the projections.
The airfoil is also commonly masked before coating to prevent the coating from flowing into the cooling slots. A grit blasting step is then employed after coating to remove any ceramic residue in the cooling slots.
A drawback to conventional shields is that the ceramic coating can leak around the shield and possibly flow into the cooling slots. Additionally, the steps of masking and grit blasting are costly. Finally, the shield does not include any feature to secure the shield relative to the airfoil.
Hence, there is a need in the art for a shield that prevents a ceramic coating from flowing into cooling slots of a vane of a gas turbine engine during a ceramic coating process and that overcomes the drawbacks and shortcomings of the prior art.